TWI675129B - Environmentally friendly nickel electroplating compositions and methods - Google Patents

Abstract

The environmentally friendly nickel plating composition is capable of electroplating nickel deposits, which are bright and uniform and suppress corrosion of the gold layer deposited on the bright and uniform nickel deposits. The environmentally friendly nickel plating composition can be used to plate bright and uniform nickel deposits on a variety of substrates over a wide range of current densities.

Description

Environmental protection nickel plating composition and method

The invention relates to an environmentally friendly nickel plating composition and method. More specifically, the present invention relates to an environmentally friendly nickel plating composition and a method for electroplating nickel on a substrate over a wide range of current densities, in which the nickel deposit is bright and uniform, and its performance can suppress the subsequent plating And the formation of holes in the gold alloy layer, thereby preventing corrosion of plated articles when nickel deposits are used as the bottom layer.

Bright nickel plating baths are used in automobiles, appliances, appliances, hardware, and various other industries. One of the most commonly known and used nickel plating baths is the Watts bath. A typical Watts bath contains nickel sulfate, nickel chloride, and boric acid. Watts baths are usually operated at a pH range of 2-5.2, a plating temperature range of 30-70 ° C, and a current density range of 1-6 amps / square decimeter. Nickel sulfate is contained in the bath in considerable amounts to provide the required nickel ion concentration. Nickel chloride improves anodic corrosion and increases electrical conductivity. The pH of the bath was maintained using boric acid as a weak buffer. To obtain bright and shiny deposits, organic and inorganic brighteners are usually added to the bath.

A common problem with most metal plating baths is the recovery of bath components and the disposal of waste products after use. Although some bath components are easy to recover, the recovery process may be expensive, but other components and decomposition products may be difficult to recover and discharged into wastewater, which may pollute the environment. In the case of Watts baths, nickel sulfate and nickel chloride are easily recovered; however, the recovery of boric acid is often challenging and often ends up with environmentally polluting wastewater.

Many governments around the world are passing stricter environmental laws and regulations that involve how to treat chemical waste and the types of chemical industries that can be used in the development and manufacturing process. For example, in the European Union, a chemical registration, evaluation, authorization, and restriction regulation called REACh prohibits many chemicals, or chemicals such as boric acid that are being banned for a large number of industrial uses. Therefore, the metal plating industry, which manufactures and sells plating baths that usually contain boric acid, attempts to develop baths that do not contain boric acid. In nickel plating baths, many manufacturers have attempted to solve the problem of developing a boric acid-free nickel plating bath with substantially the same plating properties by replacing boric acid with nickel acetate. Unfortunately, nickel acetate baths often produce rough and insufficiently dense nickel deposits that change in appearance depending on the applied current density. In addition, depending on the amount contained in the nickel bath, a nickel acetate-based bath may produce an unpleasant odor, thereby endangering the working environment.

Another compound is usually contained in a nickel plating bath to improve the plating performance, and currently many governments do not approve this compound, which is coumarin. Coumarin has been incorporated into a nickel plating bath to provide high leveling, ductility, semi-bright, and sulfur-free nickel deposits in the Watts bath. Leveling refers to the ability of nickel deposits to fill and smooth surface defects such as scratches and polishing marks. An example of a typical coumarin-containing plating bath contains about 150-200 mg / L coumarin and about 30 mg / L formaldehyde. The high concentration of coumarin in the bath has excellent leveling; however, this performance is transient. Such a high coumarin concentration results in a high rate of harmful decomposition products. Decomposition products are undesirable because they may cause uneven, matte gray areas in the sediment, which are not easily illuminated by subsequent bright nickel deposits. It reduces the leveling properties of the nickel bath, as well as other beneficial physical properties of the nickel deposits. In order to solve this problem, workers in the industry have proposed that the concentration of coumarin should be reduced and the addition of formaldehyde and chloral hydrate; however, the use of these additives at moderate concentrations will not only increase the tensile stress of nickel deposits, but also damage the Leveling performance. In addition, formaldehyde (such as boric acid and coumarin) is another compound that many government regulations (such as REACh) consider to be harmful to the environment.

It is extremely important to provide highly flat nickel deposits without sacrificing deposit ductility and internal stress. The internal stress of the nickel-plated deposit may be compressive or tensile. Compressive stress is a condition where the sediment expands to relieve stress. In contrast, tensile stress is a case of sediment shrinkage. Highly compressed deposits can cause blistering, warping, or separation of the deposits from the substrate, and high tensile stress deposits can cause warping in addition to cracking and reduced fatigue strength.

As briefly mentioned above, nickel plating baths are used in various industries. Nickel plating baths are commonly used for electroplated nickel layers on electrical connectors and lead frames. Such articles have an irregular shape and are made of metals with relatively rough surfaces, such as copper and copper alloys. Therefore, during nickel electroplating, the current density of the entire article is not uniform, often resulting in unacceptably uneven thickness and appearance of the nickel deposits throughout the article.

Another important function of the nickel plating bath is to provide a nickel base layer for gold and gold alloy deposits to prevent corrosion of the base metal of the gold plating and gold alloy. Preventing the formation of gold and gold alloy holes that cause corrosion of the underlying metal is a challenging issue. In the electronic materials industry, hole formation is particularly problematic for gold-plated and gold-plated alloy items, where corrosion can cause poor electrical contact between components in electronic devices. In electronics, gold and gold alloys are used as solderable and corrosion-resistant surfaces for contacts and connectors. Gold and gold alloy layers are also used in lead finishes for integrated circuit (IC) manufacturing. However, when gold is deposited on a substrate, certain physical properties of gold, such as its relative porosity, become problems. For example, the porosity of gold can form voids in a plated surface. These small spaces can cause corrosion or actually accelerate corrosion by the current coupling of the gold layer to the underlying base metal layer. It is believed that due to the base metal substrate and any accompanying underlying metal layers, it may be exposed to corrosive elements through holes in the outer surface of gold.

In addition, many applications include thermal exposure of coated lead frames. If the underlying metal diffuses into the precious metal surface layer, the metal diffusion between the layers may cause a loss of surface quality under thermal aging conditions.

At least three different methods have been tried to overcome the corrosion problem: 1) reducing the porosity of the coating; 2) suppressing the effects of current caused by the potential difference of different metals; and 3) sealing the holes in the plating layer. There has been extensive research into reducing porosity. Pulsed gold plating and the use of various wetting / grain refiners in gold plating baths affect the gold structure and are two factors that lead to a decrease in gold porosity. The conventional carbon bath treatment and good filtration operations are usually performed in a series of electroplating baths or tanks, and in combination with preventive maintenance programs, help to maintain gold metal deposition and correspondingly low surface porosity. However, there is still a certain degree of porosity.

Attempts have been made to hole closure, sealing, and other corrosion suppression methods with limited success. Potential mechanisms for using organic precipitates with corrosion inhibition are known in the art. Many of these compounds are generally soluble in organic solvents and are not considered to provide long-term corrosion protection. Other methods of pore closure or pore blockage are based on the formation of insoluble compounds within the pores.

In addition to the problem of hole formation, exposing gold to elevated temperatures, such as thermal aging, undesirably increases the contact resistance of gold. This increase in contact resistance affects the performance of gold as a current conductor. In theory, the staff believed that this problem was caused by the diffusion of the organic material co-deposited with gold to the contact surface. Various techniques have been tried so far to eliminate this problem, usually involving electrolytic polishing. However, no one has proven fully satisfactory for this purpose, and investigations continue.

Therefore, there is a need for a nickel plating composition and method to provide a bright and uniform nickel deposit, which has good ductility even in a wide current density range and can be used as a bottom layer to reduce or suppress pitting and gold in gold and gold alloys. The holes form a layer to prevent corrosion of the underlying metal.

The present invention relates to a nickel plating composition, which comprises one or more sources of nickel ions, one or more sources of carboxylate ions, and 2-phenyl-5-benzimidazolesulfonic acid, a salt thereof, or a mixture thereof.

The invention also relates to a method for electroplating nickel metal on a substrate, comprising: a) providing a substrate; b) combining the substrate with one or more sources of nickel ions, one or more sources of carboxylate ions, and 2-phenyl-5-benzene Contact the nickel plating composition of the imidazole sulfonic acid, a salt thereof, or a mixture thereof; and c) apply a current to the nickel plating composition and the substrate to plate a bright and uniform nickel deposit near the substrate.

The aqueous nickel plating composition is environmentally friendly. Electroplated nickel deposits are bright and uniform with good leveling. In addition, the bright and uniform nickel deposits can have good internal stress characteristics, such as reduced tensile stress and good compressive stress, so that the nickel deposits adhere well to their plated substrates. Nickel deposits plated from environmentally friendly aqueous nickel plating compositions can have good ductility. In addition, the nickel plating composition can plate bright and uniform nickel deposits over a wide range of current densities, even on irregularly shaped articles, such as electrical connectors and lead frames. Bright and uniform electroplated nickel deposits can be used as the nickel base layer of gold and gold alloy layers to suppress pitting and hole formation in gold and gold alloys, thereby preventing metal corrosion under the gold and gold alloy layers.

As used throughout the specification, unless the context clearly indicates otherwise: ° C = Celsius; g = grams; mg = milligrams; ppm = mg / L; L = liters; mL = milliliters; cm = centimeters; μm = micrometers; DI = deionized; A = ampere; ASD = ampere / square decimeter = plating speed; DC = direct current; UV = ultraviolet; lbf = pound force = 4.44822162 N; N = Newton; psi = pounds per square inch = 0.06805 atmospheres ; 1 atmosphere = 1.01325 × 10 ⁶ dyne / cm 2; wt% = weight percentage; v / v = volume ratio; C = carbon atom (element symbol) specified in the periodic table of the elements; XRF = X-ray fluorescence; SEM = Scanning electron micrograph; rpm = revolutions per minute; ASTM = American Standard Test Method; and GIMP = GNU image manipulation program.

The term "carboxylate ion" means a carboxylic acid ^{(R-COO - + H +} , wherein "R" is a C ₁ -C ₃₀ preferably has carbon atoms, more preferably C ₁ -C ₁₀ organic group of carbon atoms) of Conjugated base, and is a negatively charged ion (anion). The term "cation" means a positively charged ion having at least one (+) charge. The term "anion" means a negatively charged ion having at least one (-) charge. The term "adjacent" means that direct contact causes two metal layers to have a common interface. The term "aqueous" means water or water based. The term "leveling" means that the electroplated deposit has the ability to fill and smooth surface defects such as scratches or polishing marks. The term "matte" means dull appearance. The term "pit" or "pitting" or "hole" means a hole or opening that can completely penetrate the substrate. The term "dendrite" means a crystalline substance having a branched chain structure. The terms "composition" and "bath" are used interchangeably throughout the specification. The terms "sediment" and "layer" are used interchangeably throughout the specification. The terms "electroplating", "plating" and "deposition" are used interchangeably throughout the specification. The term "leadframe" means a metal structure inside a chip package that carries electrical signals from the die to the outside of the chip package. Throughout this specification, the terms "a" and "an" may refer to both the singular and the plural. All numerical ranges are inclusive and can be combined in any order, but such numerical ranges are logically limited to a total of 100%.

The invention relates to an environmentally friendly aqueous nickel plating composition and a method for electroplating nickel on a substrate, which provides a bright and uniform nickel deposit. The environmentally friendly aqueous nickel plating composition includes 2-phenyl-5-benzimidazolesulfonic acid, Its salts or mixtures thereof. Nickel plating compositions can be used to plate bright and uniform nickel deposits over a wide range of current densities, even on irregularly shaped articles, such as electrical connectors and lead frames. The environmentally friendly aqueous nickel plating composition has good leveling properties, and the bright and uniform nickel deposits plated by the environmentally friendly aqueous nickel plating composition have good internal stress characteristics and good ductility.

2-phenyl-5-benzimidazolesulfonic acid or a salt thereof has the formula: (I) where a cation is provided to balance the charge on the 2-phenyl-5-benzimidazolesulfonic acid anion. Salts of 2-phenyl-5-benzimidazolesulfonic acid include, but are not limited to, alkali metal salts such as lithium, sodium, and potassium salts, and nickel salts. Preferably, the cation is a hydrogen ion, a lithium ion, a sodium ion, or a potassium ion, and more preferably, the cation is a hydrogen ion, a sodium ion, or a potassium ion.

Generally, 2-phenyl-5-benzimidazolesulfonic acid, a salt thereof, or a mixture thereof is at least 25 ppm, preferably 25 ppm to 2000 ppm, more preferably 100 ppm to 2000 ppm, and most preferably An amount of 200 ppm to 2000 ppm is included in the environmentally friendly aqueous nickel plating composition of the present invention.

The aqueous nickel plating composition of the present invention contains one or more nickel ion sources in an amount sufficient to provide at least 25 g / L, preferably 30 g / L to 150 g / L, and more preferably 35 g / L to 125 g / L , Even better 40 g / L to 125 g / L, and the best 50 g / L to 125 g / L nickel ion concentration.

One or more sources of nickel ions (cations) include a water-soluble nickel salt. One or more sources of nickel ions include, but are not limited to, nickel sulfate and its hydrated form, nickel sulfate hexahydrate and nickel sulfate heptahydrate; nickel sulfamate and its hydrated form, nickel sulfamate tetrahydrate; nickel chloride and its Hydrated form, nickel chloride hexahydrate; and nickel acetate and its hydrated form, nickel acetate tetrahydrate. The environmentally friendly aqueous nickel plating composition contains one or more sources of nickel ions in an amount sufficient to provide the desired nickel ion concentration disclosed above. Nickel acetate or a hydrated form thereof may be contained in the aqueous nickel electroplating composition, preferably in an amount of 15 g / L to 45 g / L, more preferably 20 g / L to 40 g / L. When nickel sulfate is included in the aqueous nickel plating composition, it is preferred that nickel sulfamate or its hydrated form is not included. Nickel sulfate may be contained in the aqueous nickel plating composition, preferably in an amount of 100 g / L to 550 g / L, and more preferably in an amount of 150 g / L to 350 g / L. When the nickel sulfamate or its hydrated form is contained in the aqueous nickel plating composition, its content is preferably 120 g / L to 675 g / L, more preferably 200 g / L to 450 g / L. The aqueous nickel plating composition may contain nickel chloride or a hydrated form thereof, preferably in an amount of 1 g / L to 100 g / L, more preferably 5 g / L to 100 g / L, and even more preferably 5 g / L. Up to 75 g / L.

Optionally, but preferably, sodium saccharin is included in the aqueous nickel plating composition. When sodium saccharin is included in the nickel plating composition, the content is at least 100 ppm. Preferably, the content of sodium saccharin is 200 ppm to 5000 ppm, more preferably 300 ppm to 5000 ppm, and most preferably 400 ppm to 5000 ppm.

When sodium saccharin is included in the nickel plating composition of the present invention, the content of 2-phenyl-5-benzimidazole sulfonic acid and its salt is preferably 20 ppm to 1000 ppm, more preferably 100 ppm to 900 ppm, and even more 100 ppm to 800 ppm, and 100 ppm to 500 ppm.

The aqueous nickel plating composition of the present invention comprises one or more sources of carboxylate ion. The carboxylate ion (anion) of the present invention may be a mono-, di-, tri- or tetra-carboxylate ion, preferably C ₁ to C ₃₀ carbon atoms, with the limitation that it is soluble under the conditions of use, and more preferably, It is a mono or dicarboxylate ion of C ₁ to C ₁₀ carbon atoms. Carboxylate ions (anions) include, but are not limited to, acetate, formate, malate, tartrate, gluconate, benzoate, 3-sulfobenzoate, salicylate, 5-sulfosalicylate, Propionate, adipate or mixtures thereof. Preferably, the carboxylate is acetate, malate, gluconate, benzoate, 3-sulfobenzoate, salicylate, 5-sulfosalicylate or a mixture thereof, more preferably, carboxylate Is acetate, malate, gluconate, 3-sulfobenzoate, 5-sulfosalicylate or mixtures thereof, and even more preferably, the carboxylate ion (anion) is acetate, malate, glucose Acid, 5-sulfosalicylate or mixtures thereof. Most preferably, the carboxylate ion is acetate or 5-sulfosalicylate or mixtures thereof. The carboxylate ion (anion) source of the present invention includes, but is not limited to, a nickel salt, an alkali metal salt, such as a lithium salt, a sodium salt, a potassium salt, or a mixture thereof. The nickel ion, lithium ion, sodium ion, and potassium ion provide a counterbalance to the salt. cation. The carboxylic acid form can also be a source of one or more carboxylate ions (where the hydrogen ion is a cation). The carboxylic acid forms are, for example, acetic acid, formic acid, malic acid, tartaric acid, gluconic acid, benzoic acid, 3-sulfobenzoic acid, salicylic acid, 5-sulfosalicylic acid, propionic acid, and adipic acid. When an alkali metal salt is contained in the nickel plating composition, one or more of sodium carboxylate and potassium carboxylate are preferably selected, and more preferably, potassium carboxylate is selected. Sodium salts are, for example, sodium acetate, sodium formate, sodium malate, sodium tartrate, sodium gluconate, sodium benzoate, disodium 3-sulfobenzoate, sodium salicylate, disodium 5-sulfosalicylate, propionic acid Sodium and sodium adipate. The potassium salt is, for example, potassium acetate, potassium formate, potassium malate, potassium tartrate, potassium gluconate, potassium benzoate, dipotassium 3-sulfobenzoate, potassium salicylate, dipotassium 5-sulfosalicylate, Potassium propionate and potassium adipate. Preferably, a sufficient amount of one or more carboxylate ion sources of the present invention is added to an aqueous nickel plating composition to provide at least 2 g / L, preferably 2 g / L to 150 g / L, more preferably 10 g / L to 60 g / L carboxylate ion concentration.

Optionally, one or more sources (anions) of chloride ions may be included in the aqueous nickel plating composition. A sufficient amount of one or more chloride ion sources can be added to the aqueous nickel plating composition to provide 0.1 g / L to 30 g / L, preferably 1.5 g / L to 30 g / L, and most preferably 1.5 g / L to 22.5 g / L chloride ion concentration. When nickel plating is performed using an insoluble anode, such as an insoluble anode including platinum or platinized titanium, the nickel plating composition is preferably free of chloride. Sources of chlorides include, but are not limited to, nickel chloride, nickel chloride hexahydrate, hydrogen chloride, alkali metal salts such as sodium chloride and potassium chloride. Preferably, the sources of chloride are nickel chloride and nickel chloride hexahydrate. Preferably, chloride is included in the aqueous nickel plating composition.

The aqueous nickel plating composition of the present invention is acidic, and the pH may be preferably in the range of 2 to 6, more preferably 3 to 5.5, and even more preferably 4 to 5.1. Inorganic acids, organic acids, inorganic bases, or organic bases can be used to buffer the aqueous nickel plating composition. Such acids include, but are not limited to, inorganic acids such as sulfuric acid, hydrochloric acid, aminosulfonic acid, and boric acid. Organic acids such as acetic acid, aminoacetic acid, and ascorbic acid can be used. Inorganic bases, such as sodium and potassium hydroxide, and organic bases, such as different types of amines, can be used. Preferably, the buffer is selected from the group consisting of acetic acid and aminoacetic acid. Optimally, the buffer is acetic acid. Although boric acid can be used as a buffer, optimally, the aqueous nickel plating composition of the present invention is free of boric acid. Buffers can be added as needed to maintain the desired pH range.

Optionally, one or more brighteners may be included in the aqueous nickel plating composition. Optional brighteners include but are not limited to 2-butyne-1,4-diol, 1-butyne-1,4-diol ethoxylate, 1-ethynylcyclohexylamine, and propargyl alcohol . Such brighteners can be included in amounts of 0.5 g / L to 10 g / L. Preferably, such optional brighteners are not included in the aqueous nickel plating composition of the present invention.

Optionally, one or more surfactants may be included in the aqueous nickel plating composition of the present invention. Such surfactants include, but are not limited to, ionic surfactants, such as cationic and anionic surfactants, non-ionic surfactants, and amphoteric surfactants. Surfactants can be used in conventional amounts, such as from 0.05 g / L to 30 g / L.

Examples of useful surfactants are anionic surfactants such as sodium bis (1,3-dimethylbutyl) sulfosuccinate, sodium 2-ethylhexyl sulfate, dipentylsulfosuccinic acid Sodium, sodium lauryl sulfate, sodium lauryl ether sulfate, sodium dialkyl sulfosuccinate and sodium dodecylbenzene sulfonate, and cationic surfactants such as quaternary ammonium salts such as Fluoro-quaternary amine.

Other optional additives may include, but are not limited to, leveling agents, chelating agents, complexing agents, and biocides. Such optional additives may be included in conventional amounts.

Because the nickel electroplating composition of the present invention is environmentally friendly, it does not contain compounds such as coumarin, formaldehyde, and preferably does not contain boric acid. In addition, the nickel plating composition is free of allylsulfonic acid.

In addition to the unavoidable metal contamination, the aqueous nickel plating composition of the present invention is also free of any alloy metal or metal that is usually contained in a metal plating bath to brighten or improve the gloss of metal deposits. The aqueous nickel electroplating composition of the present invention deposits a bright and uniform nickel metal layer having a substantially smooth surface, with the smallest number of components in the nickel electroplating composition.

Preferably, the environmentally friendly aqueous nickel plating composition of the present invention is composed of one or more sources of nickel ions, wherein one or more sources of nickel ions provide a sufficient amount of nickel ions in solution, and nickel is plated from one or more sources of nickel ions And corresponding counter anions, 2-phenyl-5-benzimidazole sulfonic acid, salts or mixtures thereof, and corresponding cations, one or more sources of carboxylate ions (anions) and corresponding counter cations, as appropriate, saccharin sodium, Optionally one or more chloride ion sources and corresponding counter cations, optionally one or more surfactants, optionally buffers, and water.

More preferably, the environmentally friendly aqueous nickel plating composition of the present invention is composed of one or more sources of nickel ions, wherein one or more sources of nickel ions provide a sufficient amount of nickel ions in solution, and nickel is plated from one or more sources of nickel ions And corresponding counter anions, 2-phenyl-5-benzimidazole sulfonic acid, salts or mixtures thereof, one or more carboxylate ion sources (anions) and corresponding counter cations, sodium saccharin, one or more as appropriate Chloride and corresponding cations, one or more surfactants as appropriate, buffers and water as appropriate.

Even more preferably, the environmentally friendly aqueous nickel plating composition of the present invention is composed of one or more sources of nickel ions, wherein one or more sources of nickel ions provide a sufficient amount of nickel ions in solution, and electroplating from one or more sources of nickel ions Nickel and the corresponding counter anion, 2-phenyl-5-benzimidazole sulfonic acid, a salt thereof or a mixture thereof, a carboxylate ion, wherein the source of the carboxylate ion is selected from one or more of the following: acetate, malate, Gluconate, benzoate, 3-sulfobenzoate, salicylate, 5-sulfosalicylate, corresponding cations containing carboxylate anions, and acetic acid, sodium saccharin, one or more sources of chloride ions, and corresponding Cation, one or more surfactants as appropriate, buffers as appropriate, and water.

The 2-phenyl-5-benzimidazole sulfonic acid or a salt thereof of the present invention is analyzed at a low concentration of about 1 ppm using conventional UV-visible spectroscopy, which is economical for the electroplating industry Efficient and commonly used analysis tools. This allows workers in the nickel electroplating industry to more accurately monitor the concentration of 2-phenyl-5-benzimidazole sulfonic acid or its salt in the composition during electroplating, allowing the electroplating process to maintain optimal performance and provide more efficient and economical Plating method.

The environmentally friendly aqueous nickel plating composition of the present invention can be used to deposit a nickel layer on a variety of substrates, that is, conductive and semiconductor substrates. Preferably, the substrate on which the nickel layer is deposited is a copper and copper alloy substrate. Such copper alloy substrates include, but are not limited to, brass and bronze. The temperature of the nickel plating composition during the plating may be in the range of room temperature to 70 ° C, preferably 30 ° C to 60 ° C, and more preferably 40 ° C to 60 ° C. During the plating, the nickel plating composition is preferably under continuous stirring.

Generally, the nickel metal plating method includes providing an aqueous nickel plating composition and contacting the substrate with the aqueous nickel plating composition, such as by immersing the substrate in the composition or spraying the substrate with the composition. Current is applied using a conventional rectifier, where the substrate is used as a cathode and there is an opposite electrode or anode. The anode may be any conventional soluble or insoluble anode used to plate nickel metal near the surface of the substrate. The aqueous nickel plating composition of the present invention enables a bright and uniform nickel metal layer to be deposited over a wide range of current densities. Many substrates are irregular in shape and often have discontinuous metal surfaces. As a result, the current density can vary over the entire surface of such substrates, often resulting in uneven metal deposits during electroplating. Moreover, surface brightness is often irregular with the combination of matt and shiny deposits. The nickel metal plated from the nickel plating composition of the present invention enables a substantially smooth, uniform, and bright nickel deposit to be achieved on the surface of a substrate (including an irregularly shaped substrate). In addition, the environmentally friendly nickel plating composition of the present invention enables electroplating of substantially uniform and bright nickel deposits to cover scratches and polishing marks on a metal substrate.

The current density can be in the range of 0.1 ASD or higher. Preferably, the current density can be in the range of 0.5 ASD to 70 ASD, more preferably 1 ASD to 40 ASD, and even more preferably 5 ASD to 30 ASD. When the nickel plating composition is used for roll-to-roll plating, the current density can be in the range of 5 ASD to 70 ASD, more preferably 5 ASD to 50 ASD, and even more preferably 5 ASD to 30 ASD. When nickel plating is performed at a current density of 60 ASD to 70 ASD, preferably, one or more nickel ion sources are contained in the environmentally friendly nickel plating composition in an amount of 90 g / L or more, more preferably 90 g / L To 150 g / L, even more preferably 100 g / L to 150 g / L, and most preferably 125 g / L to 150 g / L.

Generally, the thickness of the nickel metal layer may be in a range of 1 μm or higher. Preferably, the thickness of the nickel layer is in a range of 1 μm to 100 μm, more preferably 1 μm to 50 μm, and even more preferably 1 μm to 10 μm.

Although the aqueous nickel plating composition of the present invention can be used to plate nickel metal layers on different types of substrates, it is preferred to use the aqueous nickel plating composition to plate the nickel underlayer. More preferably, the aqueous nickel plating composition is used to plate the nickel metal underlayer, suppress the pore formation or pitting of gold and gold alloys, and suppress the corrosion of the metal under the gold or gold alloy layer of the plated article.

The nickel metal layer is plated on the base substrate to a thickness of 1 μm to 20 μm, preferably 1 μm to 10 μm, and more preferably 1 μm to 5 μm. The substrate may include, but is not limited to, one or more metal layers of copper, copper alloys, iron, iron alloys, stainless steel; or the substrate may be a semiconductor material such as a silicon wafer or other type of semiconductor material, and optionally by electroplating technology Processes are known to make semiconductor materials sufficiently conductive to receive one or more metal layers. Copper alloys include, but are not limited to, copper / tin, copper / silver, copper / gold, copper / silver / tin, copper / beryllium, and copper / zinc. Iron alloys include, but are not limited to, iron / copper and iron / nickel. Examples of substrates that can contain a gold or gold alloy layer near the nickel metal underlayer are components of electrical devices such as printed wiring boards, connectors, bumps on semiconductor wafers, lead frames, electrical connectors, connector pins And passive components such as resistors and IC unit capacitors.

An example of a typical substrate with a nickel underlayer is a lead frame or an electrical connector, such as a connector pin, usually made of copper or a copper alloy. An example of a typical copper alloy for connector pins is beryllium / copper alloy. The underlying nickel plating is performed within the temperature range disclosed above. The current density of the nickel-plated underlayer may range from 0.1 ASD to 50 ASD, preferably 1 ASD to 40 ASD, and more preferably 5 ASD to 30 ASD.

After the nickel metal underlayer is plated near the metal, metal alloy layer, or semiconductor surface of the substrate, a gold or gold alloy layer is deposited near the nickel metal layer. Using conventional gold and gold alloy deposition methods, such as physical vapor deposition, chemical vapor deposition, electroplating, electrodeless metal plating including immersion gold plating, a gold or gold alloy layer can be deposited near the underlying nickel metal. Preferably, a gold or gold alloy layer is deposited by electroplating.

Conventional gold and gold alloy plating baths can be used to plate the gold and gold alloy layers of the present invention. An example of a commercially available hard gold alloy plating bath is RONOVEL ™ LB-300 electrolytic hard gold plating bath (available from Dow Electronic Materials, Marlborough, Mass.).

Sources of gold ions used in gold and gold alloy plating baths include, but are not limited to, potassium cyanide gold, sodium dicyanoaurate, ammonium dicyanoaurate, potassium tetracyanoaurate, sodium tetracyanoaurate, ammonium tetracyanoau , Dichloroaurate; tetrachloroauric acid, sodium tetrachloroaurate, ammonium sulfite gold, potassium sulfite gold, sodium sulfite gold, gold oxide and gold hydroxide. A conventional amount of gold source may be included, preferably 0.1 g / L to 20 g / L, or more preferably 1 g / L to 15 g / L.

Alloy metals include, but are not limited to, copper, nickel, zinc, cobalt, silver, this technology, lead, mercury, arsenic, tin, selenium, tellurium, manganese, magnesium, indium, antimony, iron, bismuth, and thallium. Typically, the alloy metal is cobalt or nickel, which provides a hard gold alloy deposit. Alloy metal sources are well known in the art. The alloy metal source is contained in the bath in a known amount, and varies greatly depending on the type of alloy metal used.

Gold and gold alloy baths may contain conventional additives such as surfactants, brighteners, leveling agents, complexing agents, chelating agents, buffering agents, and biocides. Such additives are included in conventional amounts and are well known to those skilled in the art.

In general, the current density range for plating gold and gold alloy layers can range from 1 ASD to 40 ASD, or such as 5 ASD to 30 ASD. The temperature of the gold and gold alloy plating bath can range from room temperature to 60 ° C.

After depositing a gold or gold alloy layer near a nickel metal underlayer, generally, a substrate having a metal layer undergoes thermal aging. Thermal aging can be accomplished by any suitable method known in the art. Such methods include, but are not limited to, steam aging and dry baking. The nickel metal underlayer suppresses the diffusion of less precious metals to the surface of the gold or gold alloy layer, thereby improving solderability.

The following examples are included to further illustrate the invention but are not intended to limit its scope. Example 1 (Invention) Hull Cell Plating Result of the Nickel Plating Bath and Hull Cell Plating of the Present Invention Containing 2-Phenyl-5-Benzimidazole Sulfonic Acid

Three (3) water-based nickel electroplating baths were prepared having the components shown in the following table and the amounts of each component. Table 1

Each bath was placed in a separate Hull cell, with a brass panel and a ruler along the bottom of each Hull cell, and corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating for each bath was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The bath pH was 4.6 and the bath temperature was 60 ° C. Acetate has no detectable odor. The current is 3A. A direct current was applied to deposit a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. The nickel deposits from each Hull trough appear bright and the nickel deposits appear uniform over the entire current density range. Example 2 (Invention) Nickel plating bath and Hull bath plating result of the present invention containing 2-phenyl-5-benzimidazole sulfonic acid and sodium saccharin

Seven (7) water-based nickel electroplating baths were prepared having the components shown in the following table and the amounts of each component. Table 2A Table 2B

Each bath was placed in a separate Hull cell, with a brass panel and a ruler along the bottom of each Hull cell, and corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating for each bath was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The bath pH was 4.6 and the bath temperature was 60 ° C. Acetate has no detectable odor. The current is 3A. A direct current was applied to deposit a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. The nickel deposits from each Hull trough appear bright and the nickel deposits appear uniform over the entire current density range. Example 3 (comparative) Comparative nickel plating bath and Hull bath plating results containing 1-benzylpyridinium-3-formate

Four (4) water-based nickel electroplating baths were prepared having the components shown in the following table and the amounts of each component. table 3 (II) 1-benzylpyridinium-3-formate

Each bath was placed in a separate Hull cell, with a brass panel and a ruler along the bottom of each Hull cell, and corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating for each bath was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The bath pH was 4.6 and the bath temperature was 60 ° C. Acetate has no detectable odor. The current is 3A. A direct current was applied to deposit a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. Except for nickel deposits from a bath containing 100 ppm of a conventional nickel brightener, 1-benzylpyridinium-3-formate, comparative bath 3, the brightness of the nickel deposits is across the entire current density Uneven but irregular. Example 4 (Comparative) Results of Comparative Nickel Plating Bath and Hull Cell Plating with Pyridinium Propyl Sulfonate Compound

Three (3) water-based nickel electroplating baths were prepared having the components shown in the following table and the amounts of each component. Table 4 (III); (IV); pyridinium propyl sulfonate; hydroxy pyridinium propyl sulfonate; (V) 3- (3-Aminomethylpyridin-1-yl-1-yl) propane-1-sulfonate

Each bath was placed in a separate Hull cell, with a brass panel and a ruler along the bottom of each Hull cell, and corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating for each bath was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The bath pH was 4.6 and the bath temperature was 60 ° C. Acetate has no detectable odor. The current is 3A. A direct current was applied to deposit a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. For any of the comparative baths 5-7, there was no evidence of uniform nickel plating over the entire current density range. Comparative bath 5-6 electroplated nickel deposits are interspersed with sporadic bright areas in the matt deposit area. Except for sporadic bright and matt areas, Comparative Bath 7 plating has dendrite-grown deposits. Dendrites are undesirable in electroplated articles because they can cause electrical shorts in the articles. Example 5 (comparative) Comparative nickel plating bath and Hull bath plating results containing 1-methylpyridinium-3-carboxylate

Four (4) water-based nickel electroplating baths were prepared having the components shown in the following table and the amounts of each component. table 5 (VI) 1-methylpyridinium-3-sulfonate

Each bath was placed in a separate Hull cell, with a brass panel and a ruler along the bottom of each Hull cell, and corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating for each bath was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The bath pH was 4.6 and the bath temperature was 60 ° C. Acetate has no detectable odor. The current is 3A. A direct current was applied to deposit a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. For any of Comparative Baths 8-11, there was no evidence of uniform nickel plating across the entire current density range. The deposit has bright areas interspersed with matte areas. Example 6 (Inventive) Nitric Acid Vapor Test of Hard Gold Alloy Deposits with Nickel Underlayer

Two (2) aqueous nickel plating baths were prepared with the formulations disclosed in the table below. Table 6

Thirty (30) double-sided beryllium / copper (Be / Cu) alloy connector pins with irregular surfaces were plated with a nickel plating bath 11 and a nickel plating comparison bath 12 was plated in a 1 liter plating bath and another 42 Needles. The pH of bath 11 was 4.6, and the pH of comparative bath 12 was 3.6. The temperature of the nickel plating bath was about 60 ° C. The anode is a nickel sulfide electrode. The plating was performed at a current density of 5 ASD for a sufficient time to plate a nickel layer on each connector pin to a target thickness of about 2 μm. XRF analysis was performed using a conventional XRF spectrometer to measure the thickness of nickel deposits.

After plating a layer of nickel on the connector pins, remove the pins from the bath, place them in a 10% by volume sulfuric acid solution for 30 seconds, and then transfer to a bath containing RONOVEL ™ LB-300 electrolytic hard gold A plating bath obtained from Dow Electronic Materials, Marlborough, Mass., And each connector pin was then plated with a hard gold alloy layer to a target thickness of approximately 0.38 μm.

Gold alloy plating was performed at a current density of 1 ASD at 50 ° C. The anode is a platinum-plated titanium electrode. The pH of the gold alloy bath was 4.3. After the needles are plated with gold alloy, they are removed from the plating bath and air-dried. Prior to the corrosion test, each needle was imaged to record the surface appearance of the needle. A LEICA DM13000M optical microscope was used to capture the surface image of each needle at 50x magnification. No observable signs of corrosion on any surface of the needle (both sides).

The gold alloy-plated connector pins were then exposed to nitric acid vapor, essentially in accordance with the ASTM B735-06 nitric acid vapor test, to evaluate the corrosion resistance of the nickel underlayer from both types of nickel plating baths. Each connector needle was suspended in a 500 mL glass container, where the environment in the glass container was saturated with 70% by weight nitric acid vapor at 22 ° C. The needles were exposed to nitric acid vapor for about 2 hours. The nitric acid-treated needles were then removed from the glass container, baked at 125 ° C, and then cooled in a desiccator before analysis.

A LEICA DM13000M optical microscope was used to capture the surface images (both sides) of each needle at 50x. FIG. 1 is a 50 × photograph taken with a LEICA DM13000M optical microscope, in which a connector pin of a gold alloy plating is plated with a nickel base layer from a bath 11. Only two corrosion spots (black spots) can be seen on the surface of the needle. In contrast, the needles plated with the comparative bath 12 had excessive corrosion. FIG. 2 is a 50 × photograph taken with an optical microscope, in which a connector pin of a gold alloy plating is plated with a nickel base layer from a comparison bath 12. Many corrosion spots and holes were observed on the surface of the gold alloy deposit. Spots and holes are caused by corrosion of the underlying nickel layer. The connector needles plated with the nickel base plating of the bath 11 of the present invention show significant corrosion suppression compared to the nickel base plated needles from the comparative bath 12. Example 7 (Invention) Ductility of nickel deposits

The nickel deposit electroplated from the bath 11 of the present invention disclosed in Example 6 above was subjected to an elongation test to determine the ductility of the nickel deposit. Ductility testing is basically done in accordance with the industry standard ASTM B489-85: Bend Test for Ductility of Electrodeposited and Autocatalytic Deposition Metal Coatings.

Multiple brass panels available. The brass panel was plated with 2 μm nickel from bath 11. The plating was performed at 5 ASD at 60 ° C. The plated panel was bent 180 ° around mandrels of various diameters ranging from 0.32 cm to 1.3 cm, and then examined for cracks in the deposit under a 50 × microscope. The smallest diameter tested without cracks was then used to calculate the elongation of the deposit. The elongation of the nickel deposit of bath 11 was found to be 10%, which is considered to be good ductility of the commercial nickel bath deposit. Example 8 (Invention) Nitric Acid Vapor Test of Hard Gold Alloy Deposits with Nickel Underlayer

Two (2) aqueous nickel plating baths were prepared, the first having the formula disclosed in the table below, and the second being the same as Comparative Bath 12 in Example 6 above. Table 7

The plating and analysis procedure described in Example 6 uses 100 double-sided beryllium / copper (Be / Cu) alloy connector pins with irregular surfaces plated from each bath in the same manner as bath 12 and comparative bath 12. get on. The results of the ASTM B735-06 nitric acid vapor test of Example 6 were basically reproduced using bath 12 and comparative bath 12. The connector needles plated with the nickel base plating of the bath 12 of the present invention show significant corrosion suppression compared to the nickel base plated needles from the comparative bath 12. Example 9 (Invention) Nickel plating bath containing 2-phenyl-5-benzimidazolesulfonic acid and acetic acid carboxylate anion

The nickel plating bath of the present invention has the formulation disclosed in Table 8. Table 8

The bath 13 is placed in a Hull bath, along the bottom of the Hull bath, there is a brass panel and a ruler, which are corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The pH of the bath 13 was 4.6, and the bath temperature of the bath liquid was 60 ° C. Acetate has no detectable odor. The current is 3A. A direct current was applied to produce a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. The nickel deposits appear bright, and the nickel deposits look uniform over the entire current density range. Example 10 (Invention) Nickel plating bath containing 2-phenyl-5-benzimidazolesulfonic acid and gluconic acid carboxylate anions

The nickel plating bath of the present invention has the formulation disclosed in Table 9. Table 9

The bath 14 is placed in a Hull bath, along the bottom of the Hull bath, there is a brass panel and a ruler, which are corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The pH of the bath 14 was 4.6, and the bath temperature of the bath liquid was 60 ° C. The current is 3A. A direct current was applied to produce a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. The nickel deposits appear bright, and the nickel deposits look uniform over the entire current density range. Example 11 (Invention) Nickel plating bath containing 2-phenyl-5-benzimidazolesulfonic acid and 3-sulfobenzoic acid carboxylate anion

The nickel plating bath of the present invention has the formulation disclosed in Table 10. Table 10

The bath 15 was placed in a Hull bath, and along the bottom of the Hull bath there was a brass panel and a ruler, which were corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The pH of the bath 15 was 4.6, and the bath temperature of the bath liquid was 60 ° C. The current is 3A. A direct current was applied to produce a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. The nickel deposits appear bright, and the nickel deposits look uniform over the entire current density range. Example 12 (Invention) Nickel plating bath containing 2-phenyl-5-benzimidazolesulfonic acid and 5-sulfosalicylic acid carboxylate anion

The nickel plating bath of the present invention has the formula disclosed in Table 11. Table 11

The bath 16 is placed in a Hull bath, along the bottom of the Hull bath, there is a brass panel and a ruler, which are corrected with different current densities or plating speeds. The anode is a nickel sulfide electrode. Nickel plating was performed for 5 minutes. The bath was agitated with a Hull groove paddle agitator throughout the plating period. The pH of the bath 16 was 4.6, and the bath temperature of the bath liquid was 60 ° C. The current is 3A. A direct current was applied to produce a nickel layer on a brass panel with a continuous current density range of 0.1-12 ASD. After plating, the panel was removed from the Hull bath, rinsed with deionized water and air-dried. The nickel deposits appear bright, and the nickel deposits look uniform over the entire current density range.

FIG. 1 is a 50-time photo of a gold-plated beryllium / copper alloy connector pin having a nickel base plated with a nickel plating bath of the present invention after approximately 2 hours of exposure to nitric acid vapor in accordance with ASTM B735. Figure 2 is a 50-time photo of a gold-plated beryllium / copper alloy connector pin with a nickel base plated with a comparative nickel plating bath after approximately 2 hours of exposure to nitric acid vapor in accordance with ASTM B735.

Claims (16)

A nickel plating composition includes one or more sources of nickel ions, one or more sources of carboxylate ions, and 2-phenyl-5-benzimidazolesulfonic acid, a salt thereof, or a mixture thereof. The nickel plating composition according to item 1 of the application, wherein the amount of the 2-phenyl-5-benzimidazolesulfonic acid, a salt thereof, or a mixture thereof is at least 25 ppm. For example, the nickel electroplating composition of the scope of application for patent, wherein the carboxylate ion is acetate, formate, malate, tartrate, gluconate, benzoate, 3-sulfobenzoate, salicylic acid Acid, 5-sulfosalicylate, propionate, adipate or mixtures thereof. For example, the nickel plating composition in the scope of patent application No. 1 further includes sodium saccharin. For example, the nickel plating composition of the scope of patent application 1 further includes one or more chloride sources. For example, the nickel plating composition of the scope of patent application 1 further includes one or more surfactants. For example, the nickel plating composition according to the first patent application scope, wherein the nickel plating composition has a pH of 2 to 6. A method for electroplating nickel metal on a substrate, comprising: a) providing the substrate; b) combining the substrate with one or more sources of nickel ions, one or more sources of carboxylate ions, 2-phenyl-5-benzene Contact the nickel plating composition of the imidazole sulfonic acid, a salt thereof, or a mixture thereof; and c) apply a current to the nickel plating composition and the substrate to plate a bright and uniform nickel deposit near the substrate. For example, the method of claim 8 in which the current density is at least 0.1 ASD. The method of claim 8, wherein the amount of the 2-phenyl-5-benzimidazolesulfonic acid, a salt thereof, or a mixture thereof is at least 25 ppm. The method according to item 8 of the application, wherein the carboxylate ion is acetate, formate, malate, tartrate, gluconate, benzoate, 3-sulfobenzoate, salicylate, 5 -Sulfosalicylate, propionate, adipate or mixtures thereof. The method of claim 8 wherein the nickel plating composition further includes sodium saccharin. The method of claim 8 wherein the nickel plating composition further comprises one or more chloride sources. The method of claim 8, wherein the nickel plating composition further comprises one or more surfactants. The method according to item 8 of the patent application, wherein the nickel plating composition has a pH of 2 to 6. The method of claim 8 further includes depositing a gold or gold alloy layer near the bright and uniform nickel deposit.